Major Domains of the Earth – Hydrosphere

The earth is the only planet that can sustain and nurture life. This is because of the four domains that make the planet.

What are the four major domains of the earth?

The domains, also known as the spheres are :

Lithosphere : The lithosphere is the solid, outer part of the earth and includes the brittle, upper portion of the mantle and the crust. It is bound by the atmosphere above and the asthenosphere(a part of the upper mantle), below. The lithosphere is the most rigid of earth’s layers.

Atmosphere : The atmosphere consists of 4 layers, and is responsible for the air we breathe, the weather we experience. It also protects us from the sun’s rays and regulates the temperature on the surface.

Biosphere : The biosphere connects all the existing ecosytem into a network with the other spheres.

What is hydrosphere?

Hydrosphere is the part of the earth which, combines all the water sources on the planet. It includes atmospheric water, oceans, rivers, lakes, groundwater, ice and any other possible source.

The hydrosphere incorporates the water cycle, where water travels from one source to another, changing forms temporarily in between. About 70% of the earth’s surface is covered in oceans which is not potable water. A very small percentage of earth’s water is fresh water.

What is the water cycle?

The water cycle, or the hydrological cycle, takes into account, the exchange of water from the hydrosphere, and cryosphere, which is frozen ice. The continuous movement and exchange of water helps to form currents that move warm water from the tropics to the poles and help regulate the temperature of the earth.

Although several other elements are part of the water cycle, some are useful, like oxygen, while others maybe harmful, like acid rain, algal blooms etc.

Human impact on the hydrosphere

The world’s water sources have gotten and are getting even more impacted by human lifestyle.

Massive discharge of toxic chemicals, radioactive substances and other industrial wastes, petroleum waste and sewage disposal, seepage of minerals and pesticides into the ground water are all responsible for affecting the quality of the hydrosphere.

Major threats to the hydrosphere

The hydrosphere is affected by excessive pollution of the water sources. This has caused several problems, some of them irreversible. The three major problems are :

1. Eutrophication :

Eutrophication is the excessive dumping of nutrients into water sources. This process induces growth of plants and algae which in turn depletes the oxygen levels in the water, apart from causing other probplems. Eutrophication is almost always induced by phosphate – containg detergents, fertilizers, or sewage in water.

2. Acid rain :

Acid rain is defined as precipitation, with a pH of less than 5.7 that results from reactions involving gases other than carbon dioxide. It has become a world wide problem and is caused by the emission of sulphur di-oxide and nitrogen oxides to the atmosphere by human activities, mainly, fossil fuel burning.

3. Greenhouse gases :

Green house gas emissions from the burning of fossil fuels has led to serious issues. One of them being the increase of global temperatures, which has caused melting of polar ice caps. This has caused the global environment to change considerably.

Environmental problems of hydrosphere

Some issues that we might face in the future if it is left unchecked are :